[PATCHv2 21/22] drm/bridge: tc358767: add IRQ and HPD support

[Andrzej Hajda]

On 15.04.2019 12:59, Tomi Valkeinen wrote:
> On 15/04/2019 13:42, Andrzej Hajda wrote:
>
>> Ok we have here 4 combinations:
>>
>> 1. noHPD + eDP.
>>
>> 2. noHPD + DP.
>>
>> 3. HPD + eDP.
>>
>> 4. HPD + DP.
>>
>>
>> Which ones do you want to support, disallow. It is not clear to me.
> They all should work.
>
> If there is HPD, we use it to return connected/disconnected.


OK, I though that eDP does not use HPD at all.


> If we don't have HPD:
> - If there's a panel (i.e. eDP), we presume that it is always there, as
> by definition it can't be disconnected.
> - If there's no panel (i.e. DP), we can't know if the cable is connected
> or not, so we return unknown. I think this could be improved by trying
> to "ping" the monitor with an AUX transaction, but I didn't look at that.
>
>> Moreover what connector_status_unknown should mean here for users?
> The the driver does not know if there's a monitor or not.

:)

More specifically, what user can do with such information.

OK, he can ensure monitor is connected and then force connected state.

But shall we expect existence of such configurations, I hoped we could
eliminate such combination (DP+noHPD) during probe.


>
>>> +	if (tc->hpd_num >= 0 && tc->bridge.dev) {
>>> +		bool h = val & INT_GPIO_H(tc->hpd_num);
>>> +		bool lc = val & INT_GPIO_LC(tc->hpd_num);
>>> +
>>> +		dev_dbg(tc->dev, "GPIO%d: %s %s\n", tc->hpd_num,
>>> +			h ? "H" : "", lc ? "LC" : "");
>>
>> What does "h" and "lc" mean?
> These are from the func spec. H means high, LC means low-counter. H is
> triggered immediately when the HPD line goes high, LC is triggered when
> the line has been low for the counter-specified time (the counter is
> configured at probe time).


It would be good to add this info somewhere, it is hard to guess what lc
means.


Regards

Andrzej


>
> These could be used to implement a more elaborate DP HPD & interrupt
> handling, but for the time being the driver just takes them as "HPD may
> have changed".
>
>  Tomi
>